SX-737 Project

Discussion in 'Pioneer Audio' started by Motnick, Jul 4, 2017.

  1. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    So impatience got the best of me while I wait for my mouser order to arrive, and I swapped the Q1 and Q3 transistors from the left channel with the Q2 and Q4 transistors from the right channel. My expectation was that my offset issue in the right channel would move to the left channel, but I was actually able to adjust the offset down very close to zero in both channels after swapping transistors.

    The pots are very close to being railed still, but the offset in both channels is now very close to zero (Left = 21mv, Right = 26mv).

    Perhaps I had a bad solder joint, and not a bad transistor?
     
    Last edited: Jul 7, 2017
  2. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    Did you build and use a DBT? If not, put the tools up and don't do any more board work until you have a DBT. If you short something and put it on line power, it is going to likely cause additional component failures that will make the job a lot less fun. Trust me. I shorted a pin while adjusting offset on my 1010 and it blew several transistors and burned resistors. I had to test every one of them, which required you to lift a leg on each. Not fun.
     
  3. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    Ok ok. You are right. Let me go to the hardware store now. I'll get the DBT built while I wait for the mouser order to arrive.

    Swapping the transistors without the DBT was a chance I shouldn't have taken, but the results did surprise me.
     
  4. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    Believe me I understand your anxiousness. Just don't want to see you create a mess of a working receiver. Get the DBT done while you are waiting on the parts. Start planning your work. Go through each board and ID each cap value and match it with the schematics. Make a note of any differences. Also, take good pictures of each board from different angles. Sort those by board. If you get lost you can reference the pictures. Then you can create a sheet for each board with the components that you want to replace with the values of the component. Also, most of the replacement transistors are EBC. You will need to use the silkscreen diagram on the board itself to know how to orient the replacements. If you get really bored, you can read through my SX-737 rebuild thread. The first 18 or so pages are me starting from scratch on my first rebuild and learning about equipment, soldering and how to clean up the boards: http://audiokarma.org/forums/index.php?threads/pioneer-sx-737-rebuild-bom.692191/

    When you get the parts, put the sheet on top of a piece of foam, match up the parts from your BOM and pop them through the paper in the corresponding location. This make the job more organized and less prone to mistakes. You will be ready to hit the ground running if you prep. If this is your first rebuild, its going to take you many hours. Be patient.

    Post all of your progress and you will get help along the way. There are a lot of experts here and they will be your guide.
     
  5. WE6C

    WE6C Active Member

    Messages:
    465
    Location:
    Colfax, Northern California
    If you need to make a DBT in a pinch, find a bulb socket (there's prolly one in the garage someplace), get an extension cord, cut one wire of the extension cord and hook one side up to one of the socket's terminals and the other wire to the other side/terminal. Now the socket/bulb is in series with that one wire. Screw the socket to a board. That's a 5 min DBT! Yes, in a pinch.

    When you're done with the 737 and blasting and rocking out to some of your favorite tunes, then make/build a more professional looking DBT.

    Bob
     
  6. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    Oh my god this amp sounds great! I have had it playing for the past few hours. Offset is holding tight since I swapped the transistors.

    I am really excited to hear how it sounds once I have recaped it.

    Thanks for the help of this forum. I am sure I will have will more questions once my mouser order shows up. I plan to assemble the DBT tomorrow. Then take things one board at a time now that the amp is working alright. My plan is to redo the power board and protection board first. Then move onto the amp board. Is that the best plan?
     
  7. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    Yeah that is a good plan. Like I said, take the time to plan it out and it will go smoother. There will likely be issues during the process, but people here can help you through it. You will likely lift pads unsoldering components, get transistors in wrong, etc.

    If you have patience and are methodical, it will pay off. I LOVE my 737. I think I love it more than my 1010. It's just a special receiver. What speakers are you using?
     
  8. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    Also, you should post your BOM.
     
  9. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    Some crap accoustiflex model 4 test speakers. I have a line on some Polk S8 speakers. Not the best, but a big step up from what I have currently. I'll get there one piece at a time. The entire idea is to bring myself back to the music I loved in the past. Life has gotten in the way, and the idea behind this hobby has always been to bring myself back to enjoying music like I used to in the past.
     
    Last edited: Jul 8, 2017
  10. WE6C

    WE6C Active Member

    Messages:
    465
    Location:
    Colfax, Northern California
    Glad to hear it sounds great and your voltages are hanging in there! Good job!

    Bob
     
  11. john stumpf

    john stumpf AK Subscriber Subscriber

    Messages:
    358
    Location:
    philippines
    to paraphrase jim mckay "the thrill of victory, and the agony of waiting for parts"
     
    Last edited: Jul 9, 2017
  12. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    I have read through both your 737 and your 1010 rebuild threads. Good job on both!

    I have also been researching some on soldering technics. I have watched all of the PACE videos as well. I am comfortable with soldering on the PCB, but I think I will do some practicing on other boards before I move onto my 737. My mouser order is supposed to arrive today but I am going to practice more before I proceed.

    From reading your threads it looks like you ended up using 63/37 solder? What diameter solder did you use? I have some 60/40, but will buy some 63/37 if you think I'll have better luck with it.

    Once I feel comfortable moving into the 737 my plan is to do one board at a time and checking with the DBT after each board. I have also thought about breaking each board up into sections and checking in between to reduce the amount of back tracking if I find an issue. My thoughts are to do the caps first, check with the DBT, transistors check with the DBT, diodes check with the DBT, etc. do you think this is an ok plan, or is better to just do the entire board at once?
     
    Last edited: Jul 19, 2017
  13. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    19,774
    Location:
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    Your breaking down the board into component parts is laudible, and perfectly doable for a non TECH. Do it that way and you'll be LESS confused as to what part is causing a problem when you run into one. I started doing that on my 1010, which was the 1st of my pioneers to get overhauled, and it lessened the mistakes by a whole lot. The 737 is a dreamboat to work on compared to a 1010. It's also IMO the "best bang for the buck" of any receiver in the x3x series. I listen to my 737 more than my 939 and 434(which I bought new in the Navy 1975). It just sounds better than the 939/1010 to me. The only thing the 434 gives up to the 737 is some sensitivity/selectivity in the tuner, total watts, and the extra bells and whistles in the 737.

    I would make one change to the DBT though. You'll see more of a change in the brightness of the DBT Bulb by using a 100W bulb. This is actually better for someone who has never used a DBT before. Mine has a 3-way bulb in it as I use it for a variety of amps, pre-amps, Tuners. A 50-100-150W bulb is just about perfect for 90% of Audio gear.
     
  14. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    I don't know what the diameter is. I will have to look tonight when I get home from work. Either 63/37 or 60/40 will work fine. Just use what you have. It is good to practice if you have the time. You will avoid more mistakes that way. I would say practice in desoldering is maybe more important than soldering. You don't want to over heat the joint and take off the solder pad. Otherwise you will be doing a repair like in my 737 thread. It can be tricky getting the components out. Sometimes I wiggle them while heating to break the connection while it cools.

    I can't say I ever got a cap in backwards, those are pretty easy to do. Transistors on the other hand gave me fits. I triple check them now.

    Tips for soldering, is to use flux. I use the liquid flux in a bottle with a needle applicator. Works great and you get better wetting. You want to clean all the flux off when done. Those Kemtech wipes are fantastic for soaking up flux. I ordered mine off Amazon. Use 99% alcohol if you can get it. Sometimes you may need acetone to get it all. I got 100% at the drug store.

    I think you will be better off doing an entire board. Visually check your work, then put it back in place and test on DBT. Go slow and make sure you look at your joints through a magnifying glass. Make sure you solder every connection. I usually place many component on the board, then solder them, then clean and inspect them. The more you pull a board out, the more you stress the wire connections. Sometimes they break and you have to solder them back to the pins.

    DO NOT undo the wire wraps. You should not need to do that as there is enough slack in the wires, once they are freed from the cable management clips, to get to every board.
     
  15. loweran

    loweran AK Subscriber Subscriber

    Messages:
    757
    Location:
    Austin, Texas
    So, Larry says to go ahead and break it down. Then do that. He has a ton more experience than I. The 737 was actually pretty easy once I figured out how to install a transistor. As Larry said, it's a great receiver. I like mine as much as my 1010 and better than my 838.
     
  16. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    Thanks guys. My plan is to start with the power supply board. I think that I will break it up into sections. If that goes smooothly then maybe I willl try to do the entire protection board at once. Let's see how it goes.

    I have the Technics SA-200 and the Sankyo SRC-4040 to listen to in the meantime, so no need to rush through the 737. I would rather take my time and try to avoid the mistakes that usually come from rushing ahead.

    I also picked up a set of Polk Audio S8's over the weekend so now I have some halfway decent speakers to listen to.
     
  17. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    I will also plan to post my BOM for each board before I begin. Hopefully that way you guys can help me identify any missing parts, incorrect parts, etc.
     
    Last edited: Jul 11, 2017
  18. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    I have been printing off the data sheets for all of the replacement transistors. I plan to identify any transistors that do not have the same pin out as the original on my BOM list to help me ensure that I install the new ones correctly.
     
  19. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

    Messages:
    19,774
    Location:
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    Post the BOM IN-TOTO before you Order anything. Then AFTER it's vetted for completeness, current parts vs. obsolete, better parts that have come out since the BOM was made, etc., you can make the order and save a lot on shipping.

    Good idea on the DATA Sheet's. We do suggest this. Pin order is generally Pins DOWN, Printing facing you, and Pins ordered LEFT TO RIGHT! on the TO-126 transistors the printing is hard to see, so use light from an extreme angle with a magnifying light. In Most cases the seam around the top, sides, and bottom is offset front to back with the seam toward the back, behind the center line. But I've seen the opposite so doublecheck. Q1 thru Q4 on the Main Amp board have to do with the offset (I'm having a brain fart!) so if your meter has a hFe setting insert the transistor correctly in the meter holes and let it sit for a minute (the transistors are highly sensitive to temperature, even your body heat will change the readings, so let them sit a minute or two each in the meter to settle down. Then write the number down, and try to get 4 close together (close meaning 10 or less).

    Mark the Fixer DID note in one of the later BOM's the trim pots for the bias and offset. Use those numbers. CENTER the adjuster BEFORE INSTALLING. DO THESE ABSOLUTELY LAST. Stick a note on the amp board and tape it on. That way you won't forget. When you get ready to fire it up, let us know 1st and we'll outline on how to "TICKLE THE DRAGON" on a DBT, then how to readjust before and after plugging into the wall. The values change between using a DBT and the wall straight so there is a possibility of smoke release if you don't do the procedure right.

    Larry
     
  20. Motnick

    Motnick Active Member

    Messages:
    127
    Location:
    Wyandotte Michigan
    I already ordered all of the parts. They actually arrived today. I used the BOM from another thread, and got input from this forum regarding the parts that were back ordered or obsoleted.

    http://www.audiokarma.org/forums/index.php?threads/deciding-what-caps-to-use.494440/page-2

    I will still post the BOM for each board before I begin. I can already see that the relay is WAY bigger than the original. Also the two big caps are WAY smaller than the originals. It might be easier to try to find some larger caps that will fit directly into the brackets then it will be to try to make the ones I ordered fit some how.

    Let's see when we get there. For now I think it will be easiest for me to take things one board at a time.
     
    Last edited: Jul 11, 2017

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